Using Gallium3D On AMD FirePro Workstation GPUs

OpenArena was playable on the different workstation graphics cards with the
Mesa Gallium3D "R600g" driver. The Catalyst driver here was three-times
faster on average across the spectrum of FirePro/Radeon graphics cards.

VDrift is one of the few peculiar OpenGL games where the open-source drivers
-- for both AMD and NVIDIA via Nouveau -- have equal to or better performance
on average than the binary drivers. With FirePro hardware, this is still the case.